Electric circuits of an automobile are usually supplied by a battery charged by an alternator of which the excitation current is regulated by a regulator. It is most often advantageous to subdivide the electric circuits of the automobile into a main circuit 1 and auxiliary circuits 2, the main circuit comprising the circuits for ignition, battery charging, heating, ventilation and lighting fed at substantially 14 volts, and auxiliary circuits comprising an array for rapid electric heating of the windshield, rear window, seats and infra red devices supplied at higher voltage, as a function of the rapidity sought. The supply at overvoltage of the mentioned circuits has of course a temporary character which will depend either on the timing attributable to the exterior temperature, or the temperature of cooling circuit of the automobile, or the action of the driver.
At present, the solutions proposed for assuring this supply consist either of providing a second stator winding in the alternator with an appropriate number of turns for providing the desired overvoltage or, from the alternating voltage delivered at 14 volts, to use a voltage raising transformer for supplying the auxiliary circuits.
The solutions mentioned have respectively the inconveniences in use of supplementary equipment, namely the transformer, which in fact operates for only a very small time, essentially from starting of the automobile until it and the engine are again at ambient temperature, and of the reduction of nominal power of the alternator when functioning normally from the presence of the auxiliary winding.